This invention relates generally to pressure relief valves. More particularly, the present invention relates to miniaturized relief valves employed for regulating the pressure in hydraulic or pneumatic systems.
Conventional pressure relief valves to which the invention relates typically employ a ball which is biased by a spring into sealing engagement with a conical valve seat. When the force of the fluid exerted against the ball exceeds the force of the spring, the ball is axially displaced from the valve seat to thereby commence opening of the valve. As the fluid upstream of the ball valve accelerates through the valve opening, a region of lower pressure is produced in the vicinity of the valve seat. The region of lower pressure reduces the axial force exerted by the fluid on the ball so that the ball valve tends to reseat. The opening and closing (reseating) forces may result in a phenomenon termed "valve chatter" wherein the ball valve oscillates toward and away from the valve seat in a rapid fashion. Valve chatter may present critical problems for fluid systems wherein the rate of pressure change is relatively small. The resultant lower pressure region in the vicinity of the valve seat actually results in the requirement of additional fluid pressure in excess of the opening pressure for reopening the ball valve. Consequently, there may be significant difference between the opening and closing pressures of such conventional relief valves. The fluid flow through the relief valve may also be significantly diminished for a given system pressure at system pressures which are slightly greater than the opening pressure of the relief valve. The noted low pressure reseating characteristics are also common to relief valves which employ valve elements other than balls or spheroids.